The plasma concentrations of tissue plasminogen activator (t-PA) antigen, cortisol, testosterone, dehydroepiandrosterone sulphate, FSH and LH were studied in 33 men undergoing major abdominal surgery. Significant positive correlation was found between the concentrations of t-PA antigen and cortisol, suggesting that the adrenal cortex has a role in the regulation of extrinsic fibrinolysis. These two variables, however, did not distinguish between patients with postoperative deep vein thrombosis (diagnosed by 125I-fibrinogen uptake test) and those without this complication. Such distinction was possible, however, with another steroid hormone of the adrenal cortex, dehydroepiandrosterone sulphate. At present, no explanation in terms of haemostatic mechanisms can be offered for this finding.